Zeolite structure and manufacturing method thereof

ABSTRACT

The zeolite structure is a porous zeolite structure constituted of a formed article obtained by extruding a zeolite raw material containing zeolite particles and an inorganic binding material including at least basic aluminum chloride, a ratio P 1  (P 1 =V 2 /V 1 ×100) of a volume V 2  of the inorganic binding material in the zeolite structure with respect to a volume V 1  of the zeolite structure is from 10 to 50 vol %, and a relation of equation (1) is satisfied:
 
 P 2/ P 1≦1.0  (1),
 
in which P 1  is the ratio of the volume V 2  of the inorganic binding material in the zeolite structure with respect to the volume V 1  of the zeolite structure and P 2  (P 2 =Vb/Va×100) is a ratio of volumes Vb of pores having pore diameters of 0.003 to 0.03 μm with respect to the whole pore volume Va of the zeolite structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zeolite structure, and amanufacturing method of the zeolite structure. More particularly, itrelates to a zeolite structure having an excellent mechanical strength,and a manufacturing method of the zeolite structure.

2. Description of the Related Art

It is known that zeolite is a type of silicate having a mesh crystalstructure provided with fine pores having a uniform diameter, there arepresent various chemical compositions represented by the generalformula: W_(m)Z_(n)O_(2n).sH₂O (W: sodium, potassium, calcium or thelike, Z: silicon, aluminum or the like, and s takes various values), andthere are present many kinds (types) of crystal structures havingdifferent pore shapes. Zeolite has an inherent adsorption ability,catalyst performance, solid acid characteristics, ion exchange abilityand the like based on the respective chemical compositions or crystalstructures, and is utilized in various use applications such as anadsorbing material, a catalyst, a catalyst carrier, a gas separationfilm and an ion exchanger (e.g., see Patent Documents 1 to 3).

For example, MFI-type zeolite (also referred to as “ZSM-5 type zeolite”)is provided with pores each having a size of about 0.5 nm by oxygenten-membered rings among crystals, and is utilized in a use applicationsuch as an adsorbing material for adsorbing nitrogen oxides (NOx),hydrocarbons (HC) or the like in a car exhaust gas, or a gas separationfilm for selectively separating only p-xylene from a xylene isomer.Moreover, Deca-Dodecasil 3R (DDR) type zeolite is zeolite provided withpores of about 0.44×0.36 nm by oxygen eight-membered rings amongcrystals, and is utilized in a use application such as a gas separationfilm for selectively separating/removing only carbon dioxide from anatural gas or a biological gas to improve purity of methane which isuseful as a fuel.

Moreover, for the purpose of purifying NOx or the like contained in anexhaust gas discharged from an engine for a car, an engine for aconstruction machine, an industrial stational engine, a burningapparatus or the like or adsorbing hydrocarbons or the like contained inthe exhaust gas, as a ceramic carrier (a honeycomb structure) made ofcordierite or the like and having a honeycomb shape, there is used acatalyst material onto which zeolite subjected to an ion exchangetreatment is loaded.

When zeolite is loaded onto the above ceramic carrier made of cordieriteor the like, cordierite or the like does not exert a function ofremoving NOx, a function of adsorbing hydrocarbons or the like.Therefore, when cordierite or the like is present, a pressure lossduring passing of the exhaust gas increases.

To solve this problem, there is suggested a method of forming and firinga forming raw material containing zeolite subjected to an ion exchangetreatment between cations of zeolite and metal ions, to form a honeycombstructure itself (e.g., see Patent Documents 4 and 5).

[Patent Document 1] JP-A-2007-296521

[Patent Document 2] Japanese Patent No. 3272446

[Patent Document 3] JP-A-2009-000657

[Patent Document 4] JP-A-2008-169104

[Patent Document 5] WO2009/141878A1

SUMMARY OF THE INVENTION

However, such a conventional zeolite structure has a problem that amechanical strength such as a bending strength is low. In particular,when the honeycomb structure itself is made of zeolite and is installedand used in an exhaust system of a car, the conventional zeolitestructure has a problem such as breakdown or deformation due tovibration of the car or the like.

Moreover, even in the conventional zeolite structure, when a largeamount of binding material which binds zeolite particles is contained,the mechanical strength of the structure can be improved to a certaindegree. However, the ratio of zeolite included in the zeolite structurelowers, which causes a problem that a purification performancedeteriorates.

The present invention has been developed in view of the above problem,and an object thereof is to provide a zeolite structure having anexcellent mechanical strength and a manufacturing method of the zeolitestructure.

The present inventor has intensely performed investigation to solve theabove problem of a conventional technology, and has considered that asan inorganic binding material to bind zeolite particles which becomeaggregates, a predetermined amount of the binding material containing atleast basic aluminum chloride is used to form a dense binding portion bythe inorganic binding material, thereby obtaining a zeolite structuresatisfying a relation of P2/P1≦1, in which P2 is a ratio of volumes ofpores having pore diameters of 0.003 to 0.03 μm with respect to thewhole pore volume and P1 is a ratio of a volume of an inorganic bindingmaterial with respect to a volume of the zeolite structure, to solve theabove problem, thereby completing the present invention. Specifically,according to the present invention, the zeolite structure and amanufacturing method of the zeolite structure are provided as follows.

[1] A zeolite structure comprising a formed article obtained byextruding a zeolite raw material containing zeolite particles and aninorganic binding material including at least basic aluminum chlorideand being porous, wherein a ratio P1 (P1=V2/V1×100) of a volume V2 ofthe inorganic binding material in the zeolite structure with respect toa volume V1 of the zeolite structure is from 10 to 50 vol %, and arelation of equation (1) is satisfied:P2/P1≦1.0  (1),in which P1 is the ratio of the volume V2 of the inorganic bindingmaterial in the zeolite structure with respect to the volume V1 of thezeolite structure and P2 (P2=Vb/Va×100) is a ratio of volumes Vb ofpores having pore diameters of 0.003 to 0.03 μm with respect to thewhole pore volume Va of the zeolite structure.

[2] The zeolite structure according to the above [1], wherein theinorganic binding material contained in the zeolite raw materialincludes basic aluminum chloride having an amount corresponding to 10 to30 mass % in terms of a solid content with respect to 100 mass % of thezeolite particles.

[3] The zeolite structure according to the above [1] or [2], wherein theinorganic binding material contained in the zeolite raw material furtherincludes at least one type selected from the group consisting of aluminasol, silica sol, titania sol, zirconia sol, ceria sol, boehmite,montmorillonite, hydrotalcite, hydraulic alumina, silicon resin, andwater glass.

[4] The zeolite structure according to any one of the above [1] to [3],wherein zeolite particles of at least a part of the zeolite particlesare particles made of at least one type of zeolite selected from thegroup consisting of ZSM-5 type zeolite, β-type zeolite, Y-type zeolite,mordenite type zeolite and ferrierite type zeolite.

[5] The zeolite structure according to any one of the above [1] to [4],wherein zeolite particles of at least a part of the zeolite particlesare particles made of zeolite subjected to ion exchange between cationsof zeolite and ions of at least one metal selected from the groupconsisting of copper, iron, nickel, zinc, manganese, cobalt, silver,palladium, indium, cerium, gallium, titanium and vanadium.

[6] The zeolite structure according to any one of the above [1] to [5],which is formed in a honeycomb shape including partition walls disposedto form a plurality of cells which become through channels of a fluidand which extend from one end face to the other end face.

[7] A manufacturing method of a zeolite structure, comprising: a step ofmixing zeolite particles, an inorganic binding material which binds thezeolite particles to one another, and an organic binder to prepare azeolite raw material; a step of extruding the obtained zeolite rawmaterial to obtain a formed zeolite article; and a step of firing theobtained formed zeolite article to prepare the zeolite structure,wherein the step of preparing the zeolite raw material includes thesteps of adding the inorganic binding material including basic aluminumchloride having an amount corresponding to 10 to 30 mass % in terms of asolid content to 100 mass % of the zeolite particles so that a ratio ofa volume of the inorganic binding material included in the zeolitestructure with respect to a volume of the zeolite structure obtained byfiring the formed zeolite article is from 10 to 50 vol %.

In a zeolite structure of the present invention, as an inorganic bindingmaterial to bind zeolite particles which become aggregates, apredetermined amount of the inorganic binding material containing atleast basic aluminum chloride is used, and the zeolite structuresatisfies a relation of P2/P1≦1.0, in which P2 is a ratio of volumes ofpores having pore diameters of 0.003 to 0.03 μm with respect to thewhole pore volume of the zeolite structure and P1 is a ratio of a volumeof the inorganic binding material in the zeolite structure with respectto a volume of the zeolite structure. That is, the zeolite structure ofthe present invention is provided with a dense binding portion by theinorganic binding material, and a mechanical strength, for example, abending strength of the zeolite structure constituted of a porousarticle manufactured by extrusion forming is remarkably high.

Furthermore, in a manufacturing method of the zeolite structure of thepresent invention, dense binding by the inorganic binding material isrealized, and it is possible to easily and inexpensively manufacture thezeolite structure of the present invention having an excellentmechanical strength.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing one embodiment of azeolite structure of the present invention;

FIG. 2 is an enlarged view schematically showing a binding state ofzeolite particles and an inorganic binding material in a section of thezeolite structure of FIG. 1 which is vertical to the surface thereof;and

FIG. 3 is a perspective view schematically showing another embodiment ofthe zeolite structure of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Next, a configuration for carrying out the present invention will bedescribed in detail with reference to the drawings, but it should beunderstood that the present invention is not limited to the followingembodiment, and design modification, improvement and the like areappropriately added to the present invention based on knowledge of aperson with ordinary skill without departing from the scope of thepresent invention.

(1) Zeolite Structure:

As shown in FIG. 1, an embodiment of a zeolite structure of the presentinvention is a porous zeolite structure 100 constituted of a formedarticle obtained by extruding a zeolite raw material containing aplurality of zeolite particles and an inorganic binding materialincluding at least basic aluminum chloride. Here, FIG. 1 is aperspective view schematically showing the embodiment of the zeolitestructure of the present invention, and FIG. 2 is an enlarged viewschematically showing a binding state of the zeolite particles and theinorganic binding material in a section of the zeolite structure of FIG.1 which is vertical to the surface thereof.

As shown in FIG. 2, the porous zeolite structure 100 is constituted of aporous article in which zeolite particles 32 bind to one another with aninorganic binding material 33. Specifically, the structure isconstituted of the porous article manufactured through drying and firingsteps and the like of a formed article (a formed zeolite article)obtained by extruding the above predetermined zeolite raw material. Itis to be noted that reference numerals 35 of FIG. 2 are pores (i.e.,void portions) in the porous article.

Moreover, in the zeolite structure of the present embodiment, a ratio P1(P1=V2/V1×100) of a volume V2 of the inorganic binding material in thezeolite structure with respect to a volume V1 of the zeolite structureis from 10 to 50 vol %. That is, in the porous article manufacturedthrough the drying and firing steps and the like (i.e., the firedarticle), the volume ratio P1 of the inorganic binding material in thewhole structure is from 10 to 50 vol %. It is to be noted thathereinafter, the ratio P1 will be referred to as “the inorganic bindingmaterial ratio P1”.

Furthermore, the zeolite structure of the present embodiment satisfies arelation of the following equation (1), in which P1 is “the aboveinorganic binding material ratio” and P2 is a ratio (P2=Vb/Va×100) ofvolumes Vb of pores having pore diameters of 0.003 to 0.03 μm withrespect to the whole pore volume Va of the zeolite structure. It is tobe noted that the above ratio P2 will be referred to as “the fine poreratio P2” sometimes.P2/P1≦1.0  (1)

According to such a constitution, in the zeolite structure of thepresent embodiment, dense binding by the inorganic binding material isrealized, and the porous zeolite structure constituted of a formedarticle obtained by extruding the zeolite raw material containing theinorganic binding material including at least basic aluminum chloridehas a remarkably high mechanical strength, for example, a remarkablyhigh bending strength.

More specifically, basic aluminum chloride is a water-soluble substance,and is, accordingly, present as an aqueous solution in the zeolite rawmaterial. In basic aluminum chloride having such an aqueous solutionstate (basic aluminum chloride aqueous solution), as compared with aparticulate inorganic binding material such as each type of sol orboehmite which has heretofore been used as the inorganic bindingmaterial, the aqueous solution dries to bind the zeolite particles.Therefore, a binding portion which binds the zeolite particles becomesdenser.

In consequence, as to the porous article manufactured through the dryingand firing steps, the average pore diameter of gaps formed by theinorganic binding material, i.e., fine pores (also simply referred to asthe pores) formed in the porous article increases, whereby the aboverelation of equation (1) is satisfied, in which P2 is a ratio (i.e., thefine pore ratio P2) of the volumes Vb of pores having pore diameters of0.003 to 0.03 μm with respect to the whole pore volume Va of the zeolitestructure, and P1 is the above inorganic binding material ratio.Moreover, the inorganic binding material itself binds the respectiveparticles more densely, and hence a binding portion by the inorganicbinding material becomes thick, whereby the mechanical strength, forexample, the bending strength of the zeolite structure constituted ofthe porous article becomes remarkably high.

It is to be noted that when the inorganic binding material ratio P1 iscalculated, “the volume V1 (the true volume) of the zeolite structure”is a value obtained by the following equation (2).V1=Vz+V2  (2),

V1: the volume of the zeolite structure (the true volume);

Vz: the volumes of the zeolite particles; and

V2: the volume of the (fired) inorganic binding material.

The volumes Vz of the zeolite particles and the volume V2 of the (fired)inorganic binding material can be calculated, for example, from a finestructure photograph of a section of the zeolite structure cut along apredetermined portion. More specifically, in a calculation method of theabove volume, for example, the zeolite structure is first cut, and a cutsection of the structure is polished. Next, the polished cut section isphotographed with a scanning type electron microscope or the like. It isto be noted that when the fine structure of the section is photographed,a field of view preferably includes 10 to 30 zeolite particles.

As to the obtained scanning type electron microscope photograph(hereinafter referred to as “the SEM photograph” sometimes), imageanalysis software (e.g., “Image-Pro Plus (trade name)” manufactured byMEDIA CYBERNETICS Co.) is used, and the zeolite particles and theinorganic binding material are classified to measure particle diametersor occupied area of the zeolite particles, and the occupied area of theinorganic binding material. When the particle diameters of the zeoliteparticles are measured, an average value of the diameters in at leastten fields of view (i.e., corresponding to ten SEM photographs) isobtained.

Furthermore, the volumes of the zeolite particles and the volume of the(fired) inorganic binding material are calculated from the diameters oroccupied area of the photographed zeolite particles and the occupiedarea of the inorganic binding material. Therefore, in the presentdescription, “the volumes of the zeolite particles” mean the total valueof the volumes of the respective zeolite particles, i.e., the volumewhich does not include the gaps (voids) among the zeolite particles.

Moreover, when the masses of the zeolite particles and inorganic bindingmaterial to be used in a raw material stage (i.e., a manufacturingstage) are beforehand known, or when the volume of each raw materialcomponent can be measured in the manufacturing stage, the inorganicbinding material ratio P1 may be calculated in the raw material stage.When the inorganic binding material ratio P1 is obtained by such amethod, the inorganic binding material ratio P1 is remarkably easy toobtain. Hereinafter, a method of calculating the inorganic bindingmaterial ratio P1 in the raw material stage will be described.

“Vz: the volumes of the zeolite particles” in the above equation (2) canbe obtained by the following equation (3).Vz=Mz/Dz  (3),

Vz: the volume of the zeolite particles;

Mz: the mass of the zeolite particles; and

Dz: the density of zeolite (1.85 g/cm³).

Moreover, “V2: the volume of the (fired) inorganic binding material” inthe above equation (2) can be obtained by the following equation (4). Itis to be noted that in the following equation (4), “M_(B2): the mass ofthe fired inorganic binding material” is a value obtained by thefollowing equation (5). “D_(B2): the density of the fired inorganicbinding material” in the following equation (4) and “m_(B): the masschange ratio of the inorganic binding material before/after firing” inthe following equation (5) are values beforehand obtained by using andfiring only the inorganic binding material.V2=M _(B2) /D _(B2)  (4),

V2: the volume of the fired inorganic binding material;

M_(B2): the mass of the fired inorganic binding material; and

D_(B2): the density of the fired inorganic binding material.M _(B2) =M _(B1) ×m _(B)  (5),

M_(B2): the mass of the fired inorganic binding material;

M_(B1): the mass of the inorganic binding material before fired; and

m_(B): the mass change ratio of the inorganic binding materialbefore/after fired.

Moreover, when the fine pore ratio P2 is calculated, “the whole porevolume Va of the zeolite structure” is the pore volume (cc/g) per unitmass of the pores having pore diameters of 0.003 to 180 μm, and “thevolume Vb of the pores having pore diameters of 0.003 to 0.03 μm” is thepore volume (cc/g) per unit mass of the pores having pore diameters of0.003 to 0.03 μm.

It is to be noted that the above “whole pore volume Va of the zeolitestructure” and “the volume Vb of the pores having the pore diameters of0.003 to 0.03 μm” are values measured by mercury porosimetry. It is tobe noted that the pore volume can be measured with a fully automaticmultifunctional mercury porosimeter “PoreMaster 60GT (trade name)”manufactured by Quantachrome Co.

It is to be noted that if the inorganic binding material ratio P1 isless than 10 vol %, the amount of the inorganic binding material isexcessively small, it becomes difficult to satisfactorily bind thezeolite particles to one another, and the mechanical strength of thezeolite structure remarkably lowers. On the other hand, if the inorganicbinding material ratio P1 exceeds 50 vol %, the amount of the inorganicbinding material is excessively large, and the relative ratio of thezeolite particles lowers. In consequence, zeolite functionality such aspurification performance for purifying an NOx gas or the like oradsorption performance for adsorbing hydrocarbons or the like remarkablylowers.

Moreover, in the zeolite structure of the present embodiment, the value(i.e., “P2/P1”) of the ratio of “the fine pore ratio P2” with respect to“the inorganic binding material ratio P1” needs to be 1 or less. Thatis, “the inorganic binding material ratio P1” and “the fine pore ratioP2” need to satisfy the relation of the above equation (1). If the valueP2/P1 exceeds 1, the fine pore ratio P2 becomes excessively large withrespect to the inorganic binding material ratio P1, whereby themechanical strength, for example, the bending strength of the zeolitestructure lowers sometimes. It is to be noted that the mechanicalstrength of the zeolite structure also changes in accordance with thezeolite amount in the zeolite structure (i.e., the amount of the zeoliteparticles). Therefore, if “the fine pore ratio P2” is only determined,an effect of improving the mechanical strength of the zeolite structureis not necessarily developed. In the zeolite structure of the presentembodiment, when the value (i.e., “P2/P1”) of the ratio of “the finepore ratio P2” with respect to “the inorganic binding material ratio P1”is defined, the zeolite structure having a small fine pore volume in aspecific zeolite amount can be obtained. In consequence, the zeolitestructure has an excellent mechanical strength.

(1-1) Zeolite Particles:

The zeolite particles become aggregates of the zeolite structure of thepresent embodiment. As to such zeolite particle, the inorganic bindingmaterial binds the zeolite particles to one another, thereby forming onestructure.

There is not any special restriction on the zeolite particles which areused in the zeolite structure of the present embodiment, and particlesmade of heretofore known zeolite can be used. There is not any specialrestriction on the type of zeolite or the like, but zeolite particles ofat least a part of a plurality of particles are preferably particlesmade of at least one type of zeolite selected from the group consistingof ZSM-5 type zeolite, β-type zeolite, Y-type zeolite, mordenite typezeolite and ferrierite type zeolite. Among these type of zeolite, ZSM-5type zeolite and β-type zeolite are preferable, because such type ofzeolite has satisfactory purification performance and adsorptionperformance. The zeolite particles may be particles made of one type ofzeolite among the above types of zeolite, or a mixture of a plurality oftypes of zeolite particles.

There is not any special restriction on the size of the zeoliteparticles, but the average particle diameter is preferably from 0.1 to100 μm, further preferably from 0.5 to 50 μm and especially preferablyfrom 0.7 to 20 μm. If the average particle diameter of the zeoliteparticles is less than 0.1 μm, heat resistance lowers sometimes. If theaverage particle diameter exceeds 100 μm, the zeolite particles areexcessively large during the extrusion of the zeolite raw materialcontaining the zeolite particles, whereby it may become difficult toextrusion-form the zeolite structure.

It is to be noted that the average particle diameter of the zeoliteparticles can be obtained by measuring the particle diameters of thezeolite particles from an SEM photograph which is used for calculationof the above volumes of the zeolite particles (i.e., the calculation ofthe inorganic binding material ratio P1) by use of the above imageanalysis software to obtain the particle size distribution of thezeolite particles. It is to be noted that during the measurement of theparticle diameters by the above image analysis software, the diametersof round particles can be measured as the particle diameters of theparticles. Moreover, when the particle diameters of the zeoliteparticles are measured, an average value of the diameters in at leastten fields of view (i.e., corresponding to ten SEM photographs) isobtained.

Moreover, when the average particle diameter of the zeolite particleswhich are used in a raw material stage (i.e., a manufacturing stage) arepossible to be measured, the average particle diameter of the zeoliteparticles can be measured in this raw material stage. When the averageparticle diameter of the zeolite particles is obtained by such a method,the average particle diameter can remarkably easily be obtained. “Theaverage particle diameter” in the present embodiment is a mediandiameter (d50) in the particle diameter distribution of particles (e.g.,zeolite particles). It is to be noted that the average particle diameteris a value measured by a laser diffraction scattering process inconformity to JIS R1629. The average particle diameter of the zeoliteparticles can be measured with a laser diffraction/scattering typeparticle size distribution measuring device: “LA-920 (trade name)”manufactured by Horiba, Ltd.

Moreover, the zeolite structure of the present embodiment is preferablymade of zeolite (zeolite particles) subjected to ion exchange betweencations of zeolite and metal ions. Such zeolite subjected to the ionexchange between cations of zeolite and the metal ions has an excellentcatalyst function, and a treatment such as removal of nitrogen oxides(NOx) from an exhaust gas can satisfactorily be performed.

Specifically, the zeolite particles of at least a part of the pluralityof zeolite particles are preferably particles made of zeolite subjectedto ion exchange between cations of zeolite and ions of at least one typeof metal selected from the group consisting of copper, iron, nickel,zinc, manganese, cobalt, silver, palladium, indium, cerium, gallium,titanium and vanadium. For example, ion exchange between cations ofzeolite and the iron ions or copper ions can obtain a satisfactory NOxgas purification performance, or ion exchange between cations of zeoliteand the copper ions or silver ions can develop a satisfactoryhydrocarbon adsorption ability.

It is to be noted that there is not any special restriction on an ionexchange amount between cations of zeolite and the metal ions (M+/Al ionmolar ratio), but the ion exchange amount is preferably from 0.3 to 2.0,further preferably from 0.7 to 1.5 and especially preferably from 0.9 to1.2. It is to be noted that the ion exchange amount can be measuredwith, for example, an inductively coupled plasma mass analysis device:“SPQ9000 (trade name)” manufactured by Seiko Instruments, Inc. It is tobe noted that the above ion exchange amount is a molar ratio (“M+/Alions”) of a metal ion valence (M+) with respect to aluminum ions (Alions) in zeolite. It is to be noted that if the ion exchange amount issmall (e.g., less than 0.3), a catalyst performance lowers. On the otherhand, if the ion exchange amount is excessively large (e.g., exceeding2.0), the catalyst performance is saturated, and the effect due to theion exchange is not easily developed sometimes. It is to be noted thatthe ion exchange amount can be represented by the ratio (mass %) of themass of the metal ions with respect to the mass of the zeolite particlessubjected to the exchange.

It is to be noted that when the zeolite particles are subjected to theion exchange, zeolite having a powder material state before binding withthe binding material may be subjected to the ion exchange, or zeolitehaving a zeolite structure state after binding with the binding materialmay be subjected to the ion exchange. It is to be noted that because ofsimpler manufacturing steps, zeolite having the powder material state ismore preferably subjected to the ion exchange (i.e., zeolite having araw material state and beforehand subjected to the ion exchange).

(1-2) Inorganic Binding Material:

The inorganic binding material is a binding material which binds theabove-mentioned zeolite particles, which are aggregates, to one another.

In the zeolite structure of the present embodiment, as described above,a ratio P1 (P1=V2/V1×100) of a volume V2 of the inorganic bindingmaterial in the zeolite structure with respect to a volume V1 of thezeolite structure is from 10 to 50 vol %. Furthermore, as the inorganicbinding material which is, used during the preparation of the zeoliteraw material (the inorganic binding material before dried and fired), aninorganic binding material including at least basic aluminum chloride isused. It is to be noted that basic aluminum chloride as the inorganicbinding material which is used during the preparation of the zeolite rawmaterial is present as the inorganic binding material having the stateof aluminum oxide in the porous article (the zeolite structure), whenthe extrusion-formed article is fired.

Basic aluminum chloride is a water-soluble substance, and is,accordingly, present as the inorganic binding material having the stateof an aqueous solution in the zeolite raw material. Basic aluminumchloride (the aqueous basic aluminum chloride solution) having such astate of aqueous solution has heretofore been used as the inorganicbinding material. Unlike a particulate inorganic binding material suchas each type of sol or boehmite, the aqueous solution dries to bind thezeolite particles, whereby a binding portion which binds the zeoliteparticles become denser. In consequence, the binding portion by theinorganic binding material becomes thick (i.e., the binding portionbecomes dense), and the amount of pores having comparatively small porediameters (specifically, the pores having pore diameters of 0.003 to0.03 μm) becomes small, whereby the mechanical strength, for example,the bending strength of the zeolite structure constituted of the porousarticle becomes remarkably high.

It is to be noted that the ratio P1 of the volume V2 of the inorganicbinding material in the zeolite structure with respect to the volume V1of the zeolite structure is from 10 to 50 vol %, preferably from 10 to30 vol %, and further preferably from 15 to 25 vol %. According to sucha constitution, both improvement of the mechanical strength andimprovement of functionality of zeolite can be achieved with goodbalance. That is, if the inorganic binding material ratio P1 is lessthan 10 vol %, the mechanical strength of the zeolite structure lowerssometimes. If the ratio exceeds 50 vol %, the amount of the inorganicbinding material becomes large, and the functionality of the zeolitelowers sometimes.

It is to be noted that the inorganic binding material contained in thezeolite raw material preferably includes basic aluminum chloride havingan amount which is from 10 to 30 mass %, further preferably from 15 to30 mass %, and especially preferably from 20 to 30 mass % in terms of asolid content with respect to 100 mass % of the zeolite particles.According to such a constitution, the amount of basic aluminum chloridewhich forms the dense binding portion can sufficiently be acquired, andthe mechanical strength of the zeolite structure can satisfactorilyimprove. Moreover, when such an amount of basic aluminum chloride isincluded, the value of the ratio of “the fine pore ratio P2” withrespect to the above “inorganic binding material ratio P1” can be set tobe 1 or less (i.e., satisfy the relation of the above equation (1)). Itis to be noted that if the amount of basic aluminum chloride is lessthan 10 mass % in terms of the solid content with respect to 100 mass %of the zeolite particles, the mechanical strength of the zeolitestructure cannot sufficiently improve. If the amount exceeds 30 mass %,the function of the organic binder contained in the zeolite raw materialis disturbed, and water retention properties lower, whereby it maybecome difficult to extrude the zeolite raw material.

It is to be noted that the above “in terms of the solid content” means aresidual content excluding a component which is present as a liquid atordinary temperature (20° C.). That is, “the mass in terms of the solidcontent” is the mass corresponding to the solid content of the inorganicbinding material included in a solution such as the aqueous solutionwhich is the inorganic binding material. For example, the mass of basicaluminum chloride is a mass [Al₂(OH)_(n)Cl_(6-n)]_(m) (with the provisothat 0<n<6, and 1≦m≦10). For example, when basic aluminum chloride isthe aqueous solution, the mass in terms of the solid content is the massof the dried article (the solid content) in a case where the article isdried at 120° C. in the atmospheric air for 24 hours.

The inorganic binding material contained in the zeolite raw material mayfurther include another inorganic binding material in addition to basicaluminum chloride described above. Examples of this inorganic bindingmaterial include at least one type selected from the group consisting ofalumina sol, silica sol, titania sol, zirconia sol, ceria sol, boehmite,montmorillonite, hydrotalcite, hydraulic alumina, silicon resin, andwater glass.

(1-3) Zeolite Raw Material:

The zeolite raw material is a raw material for obtaining the formedarticle to form the zeolite structure of the present embodiment, andcontains the zeolite particles and the inorganic binding material asdescribed above.

It is to be noted that the zeolite raw material preferably containswater. The content of water in the zeolite raw material is preferablyfrom 30 to 70 mass % with respect to 100 mass % of the zeoliteparticles.

Moreover, the zeolite raw material may contain an organic binder, andmay further contain a dispersant and the like. Examples of the organicbinder include hydroxypropyl methylcellulose, hydroxyethylmethylcellulose, methylcellulose, hydroxyethyl cellulose,carboxymethylcellulose, and polyvinyl alcohol. It is to be noted that inthe zeolite structure of the present embodiment, hydroxypropylmethylcellulose or hydroxyethyl methylcellulose can preferably be used.Such an organic binder has a high compatibility with the aqueous basicaluminum chloride solution, whereby the function of the organic binderis not easily disturbed. Therefore, the water retention properties ofthe zeolite raw material can satisfactorily be kept. Examples of thedispersant include fatty acid, acrylic acid, sorbitan acid, dextrin andpolyalcohol.

(1-4) Zeolite Structure:

The zeolite structure of the present embodiment is constituted of aformed article obtained by extruding a zeolite raw material containingthe zeolite particles and the inorganic binding material as describedabove, and is a porous article formed by binding the zeolite particleswith the inorganic binding material. More specifically, the zeolitestructure is constituted of a fired article obtained by firing the aboveformed article.

It is to be noted that the porosity and pore diameters (fine porediameters) of the zeolite structure of the present embodiment need to beconsidered from two viewpoints. In the first viewpoint, zeolite (thezeolite particles) is a substance having fine pores as a crystalstructure. Therefore, the first viewpoint relates to fine pores having avalue inherent in the type of zeolite. The value is determined, when thetype of zeolite is determined. For example, ZSM-5 type zeolite has finepores of oxygen ten-membered rings, and fine pore diameters are fromabout 0.5 to 0.6 nm. Moreover, β-type zeolite has fine pores of oxygentwelve-membered rings, and fine pore diameters are from about 0.5 to0.75 nm. In the second viewpoint, the zeolite structure includes thezeolite particles (zeolite crystal particles) integrated with thebinding material, and hence the second viewpoint relates to the porosityand pore diameters of the zeolite structure (the porous article).

In the zeolite structure of the present embodiment, the porosity ispreferably from 20 to 60%, further preferably from 30 to 50%, andespecially preferably from 30 to 40%. It is to be noted that theporosity is a value calculated by the following equation (6) by use of apore volume per unit mass of pores having pore diameters of 0.003 to 180μm measured by mercury porosimetry, and density of the zeolitestructure.Porosity=[density of zeolite structure]/[density of zeolitestructure+1/pore volume]×100  (6)

It is to be noted that the pore volume was measured with a fullyautomatic multifunctional mercury porosimeter “PoreMaster 60GT (tradename)” manufactured by Quantachrome Co. Moreover, as to the density ofthe zeolite structure, the density of the zeolite particles was set to1.85 g/cm³, and the density of the fired inorganic binding material wasmeasured with a dry type automatic densimeter “Accupyc 1330 (tradename)” manufactured by Micromeritics, Inc. The density of the zeolitestructure was calculated by dividing the total value of the mass of thezeolite particles and the mass of the fired inorganic binding materialby the total value of the volume of the zeolite particles and the volumeof the fired inorganic binding material.

It is to be noted that in the zeolite structure of the presentembodiment, as described above, the inorganic binding material ratio P1and the fine pore ratio P2satisfy the relation of the above equation(1), but the lower limit value of the value (P2/P1) of the ratio of thefine pore ratio P2 with respect to the inorganic binding material ratioP1 is, for example, 0.01 in a manufacturable range. It is to be notedthat there is not any special restriction on the above value of theratio (P2/P1). However the ratio is preferably from 0.01 to 0.7, andfurther preferably from 0.01 to 0.5. According to such a constitution,the mechanical strength of the zeolite structure can further improve.

There is not any special restriction on the shape of the zeolitestructure, as long as the structure is formed by extrusion and can beutilized for gas purification or separation. For example, the zeolitestructure may have a shape such as a film-like shape, a plate-like shape(e.g., see FIG. 1) or a tubular shape. As shown in FIG. 3, the zeolitestructure may be formed in a honeycomb shape including partition walls 1disposed to form a plurality of cells 2 which become through channels ofa fluid and which extend from one end face 11 to the other end face 12(a zeolite structure 100 a). Here, FIG. 3 is a perspective viewschematically showing another embodiment of the zeolite structure of thepresent invention.

According to such a honeycomb shape, it is possible to form, by thezeolite structure, a honeycomb structure for purifying an exhaust gasdischarged from an engine for a car, an engine for a constructionmachine, an industrial stational engine, a burning apparatus or the likeand containing NOx or the like, or for adsorbing hydrocarbons or thelike. That is, it is not necessary to use a ceramic carrier ofcordierite or the like, which has heretofore been used. Therefore,unlike a case where the ceramic carrier is used, a pressure loss canremarkably be low. Therefore, more catalysts can be loaded on thezeolite structure. Moreover, the zeolite structure of the presentembodiment has a remarkably high strength. Therefore, even when thezeolite structure is installed and used in an exhaust system of a car,breakdown or deformation due to vibration or the like does not easilyoccur.

Moreover, when the zeolite structure is formed in the honeycomb shape,an area of a section which is perpendicular to an extending direction ofthe cells 2 is preferably from 300 to 200000 mm². If the area is smallerthan 300 mm², an area where the exhaust gas can be treated becomes smallsometimes. Additionally, the pressure loss increases sometimes. If thearea is larger than 200000 mm², the strength of the zeolite structurelowers sometimes.

Furthermore, as shown in FIG. 3, the zeolite structure 100 a of thepresent embodiment preferably comprises an outer peripheral wall 4disposed to surround the whole outer periphery of the partition walls 1.The material of the outer peripheral wall does not necessarily have tobe the same material as that of the partition walls. However, if thematerial of an outer peripheral portion is noticeably different in theviewpoints of physical properties such as heat resistance and thermalexpansion coefficient, a problem of breakdown of the partition walls orthe like occurs sometimes. Therefore, the outer peripheral wall and thepartition walls mainly preferably include the same material or contain amaterial having the equivalent physical properties. The outer peripheralwall may be formed integrally with the partition walls by extrusion, orthe outer peripheral portion of a formed article may be processed in adesirable shape and coated with the outer peripheral wall.

In the zeolite structure having the honeycomb shape, there is not anyspecial restriction on the shape of each cell (i.e., the shape of thesection of each cell which is perpendicular to a cell extendingdirection), and examples of the shape include a triangular shape, aquadrangular shape, a hexagonal shape, an octagonal shape, a roundshape, and a combination of these shapes.

The thicknesses of the partition walls in the zeolite structure havingthe honeycomb shape are preferably from 50 μm to 2 mm, and furtherpreferably from 100 μm to 350 μm. If the thicknesses are smaller than 50the strength of the zeolite structure lowers sometimes. If thethicknesses are larger than 2 mm, the purification performance lowerssometimes, or the pressure loss increases sometimes when the gas passesthrough the zeolite structure. Moreover, the thickness of the outerperipheral wall 4 of the outermost periphery of the zeolite structurehaving the honeycomb shape is preferably 10 mm or less. If the thicknessis larger than 10 mm, an area to perform an exhaust gas purificationtreatment may become small.

Moreover, there is not any special restriction on the cell density ofthe zeolite structure having the honeycomb shape, but the cell densityis preferably from 7.8 to 155.0 cells/cm², and further preferably from31.0 to 93.0 cells/cm². If the cell density is larger than 155.0cells/cm², the pressure loss increases sometimes when the gas passesthrough the zeolite structure. If the cell density is smaller than 7.8cells/cm², the area to perform the exhaust gas purification treatmentbecomes small sometimes.

There is not any special restriction on the whole shape of the zeolitestructure having the honeycomb shape, and examples of the shape includea cylindrical shape, an oval shape and another desirable shape. As tothe size of the zeolite structure, when the zeolite structure has, forexample, a cylindrical shape, the diameter of the bottom surface of thestructure is preferably from 20 to 500 mm, and further preferably from70 to 300 mm. Moreover, the length of the zeolite structure in a centralaxis direction is preferably from 10 to 500 mm, and further preferablyfrom 30 to 300 mm.

(2) Manufacturing Method of Zeolite Structure:

Next, one embodiment of a manufacturing method of the zeolite structureof the present invention will be described. The embodiment of themanufacturing method of the zeolite structure of the present inventionmanufactures one embodiment of the above zeolite structure of thepresent invention.

The manufacturing method of the zeolite structure of the presentembodiment comprises a step of mixing a plurality of zeolite particles,an inorganic binding material which binds the zeolite particles to oneanother, and an organic binder, to prepare a zeolite raw material(hereinafter referred to as “the zeolite raw material preparation step”sometimes); a step of extruding the obtained zeolite raw material toobtain a formed zeolite article (hereinafter referred to as “theextrusion forming step” sometimes); and a step of firing the obtainedformed zeolite article to prepare the zeolite structure (hereinafterreferred to as “the firing step” sometimes).

Furthermore, in the manufacturing method of the zeolite structure of thepresent embodiment, the inorganic binding material containing basicaluminum chloride having an amount which is from 10 to 30 mass % interms of a solid content with respect to 100 mass % of the zeoliteparticles is added so that the volume ratio of the inorganic bindingmaterial included in the zeolite structure with respect to the volume ofthe zeolite structure obtained by firing the article is from 10 to 50vol %, whereby the zeolite raw material is prepared.

According to such a constitution, the zeolite structure of the presentembodiment described above can simply and inexpensively be manufactured.It is to be noted that there is not any special restriction on the shapeof the formed zeolite article obtained by the extrusion, and the shapemay be a plate-like shape of the zeolite structure 100 shown in FIG. 1,or a honeycomb shape of the zeolite structure 100 a shown in FIG. 3.

Hereinafter, the manufacturing method of the zeolite structure of thepresent embodiment will be described in more detail.

(2-1) Zeolite Raw Material Preparation Step:

First, in the manufacturing method of the zeolite structure of thepresent embodiment, plurality of zeolite particles, the inorganicbinding material which binds the zeolite particles to one another, andthe organic binder are mixed to prepare the zeolite raw material. Inthis case, as described above, the inorganic binding material containing“basic aluminum chloride having an amount which is from 10 to 30 mass %in terms of a solid content with respect to 100 mass % of the zeoliteparticles” is prepared as the inorganic binding material, and added sothat the volume ratio of the inorganic binding material included in thezeolite structure (i.e. the volume ratio of the fired inorganic bindingmaterial) with respect to the volume of the zeolite structure obtainedby firing the article (i.e., the volume of the fired zeolite structure)is from 10 to 50 vol %. It is to be noted that the volume of the firedzeolite structure and the volume of the fired inorganic binding materialcan be calculated by the above equations (2) to (5). For example, theonly inorganic binding material to be used is fired to obtain a masschange ratio before and after firing the inorganic binding material,whereby the amount of the inorganic binding material which is used inthe zeolite raw material (the mass or the volume calculated from themass) is preferably determined.

As the zeolite particles, there can be used particles made of at leastone type of zeolite selected from the group consisting of ZSM-5 typezeolite, β-type zeolite, Y-type zeolite, mordenite type zeolite andferrierite type zeolite. It is to be noted that these zeolite particlespreferably have a constitution similar to that described in theembodiment of the zeolite structure of the present invention.

Moreover, the zeolite particles may be subjected to an ion exchangetreatment between the cations of particles and metal ions. When suchzeolite particles are used, a zeolite structure having an excellentcatalyst function can easily be manufactured. It is to be noted that theion exchange treatment can be performed after manufacturing the zeolitestructure.

It is to be noted that a method of subjecting the zeolite particles orthe zeolite structure to the ion exchange treatment between cations ofzeolite and the metal ions can be performed as follows.

A solution for ion exchange containing metal ions for the ion exchange(the solution containing the metal ions) is prepared. For example, whenthe ion exchange is performed by using silver ions, an aqueous solutionof silver nitrate or silver acetate is prepared. Moreover, when the ionexchange is performed by using copper ions, an aqueous solution ofcopper acetate, copper sulfate or copper nitrate is prepared.Furthermore, when the ion exchange is performed by using iron ions, anaqueous solution of iron sulfate or iron acetate is prepared. Theconcentration of the solution for ion exchange is preferably from 0.005to 0.5 (mol/liter). Moreover, the zeolite particles are immersed in thesolution for ion exchange. Immersion time can appropriately bedetermined in accordance with the intended amount of the metal ions forthe ion exchange or the like. Furthermore, when the zeolite particlesare taken out of the solution for ion exchange, dried and calcinated,the zeolite particles subjected to the ion exchange can be obtained.Drying conditions are preferably from 80 to 150° C. and from one to tenhours. Calcinating conditions are preferably from 400 to 600° C. andfrom one to ten hours.

Next, the inorganic binding material includes at least basic aluminumchloride, and may further include at least one type selected from thegroup consisting of alumina sol, silica sol, titania sol, zirconia sol,ceria sol, boehmite, montmorillonite, hydrotalcite, hydraulic alumina,silicon resin, and water glass.

It is to be noted that the amount of the inorganic binding material inthe zeolite raw material is set so that the volume ratio of theinorganic binding material included in the zeolite structure withrespect to the volume of the zeolite structure obtained by firing thearticle is from 10 to 50 vol %, preferably from 10 to 30 vol %, andfurther preferably from 15 to 25 vol %. According to such aconstitution, both improvement of the mechanical strength of theobtained zeolite structure and improvement of the functionality ofzeolite can be acquired with good balance.

Moreover, this inorganic binding material includes basic aluminumchloride having an amount which is from 10 to 30 mass % in terms of asolid content with respect to 100 mass % of the zeolite particles,whereby the amount of basic aluminum chloride which forms the densebinding portion can sufficiently be acquired, and the mechanicalstrength of the zeolite structure can satisfactorily improve. It is tobe noted that as described above, the whole amount of the inorganicbinding material to be used is calculated from the volumes of the firedzeolite structure and inorganic binding material, but the content ofbasic aluminum chloride is calculated by the mass of the solid contentin the zeolite raw material (the mass of a dried article).

It is to be noted that when the inorganic binding material includes theabove amount of basic aluminum chloride, the value (i.e., “P2/P1”) ofthe ratio of the “the fine pore ratio P2” with respect to “the inorganicbinding material ratio P1” can be set to be 1 or less. That is, it ispossible to easily manufacture the zeolite structure which satisfies theabove relation of the equation (1) between “the inorganic bindingmaterial ratio P1” and “the fine pore ratio P2”. It is to be noted thatif the mass of the solid content of basic aluminum chloride is less than10 mass % with respect to 100 mass % of the zeolite particles, themechanical strength of the zeolite structure cannot sufficientlyimprove. If the mass exceeds 30 mass %, the function of the organicbinder contained in the zeolite structure is disturbed, and the waterretention properties lower. Therefore, it may become difficult toextrude the zeolite raw material.

It is to be noted that basic aluminum chloride in the inorganic bindingmaterial preferably has an amount which is preferably from 15 to 30 mass% and further preferably from 20 to 30 mass % in terms of the solidcontent with respect to 100 mass % of the zeolite particles.

It is to be noted that basic aluminum chloride as the inorganic bindingmaterial is dissolved in water included in the zeolite raw material, andis present in the state of the aqueous solution in the zeolite rawmaterial. Therefore, a powder-like material can be used as basicaluminum chloride, but the material having preliminary the state of theaqueous solution is preferably used so that basic aluminum chloride isnot insoluble. Examples of basic aluminum chloride include “Takibine#1500 (trade name): liquid” and “Takibine #3000 (trade name): powder”manufactured by Taki Chemical Co., Ltd.

The zeolite raw material preferably contains water. The content of waterin the zeolite raw material is preferably from 30 to 70 mass % withrespect to 100 mass % of the zeolite particles.

Moreover, the zeolite raw material contains an organic binder. Examplesof the organic binder include hydroxypropyl methylcellulose,hydroxyethyl methylcellulose, methylcellulose, hydroxyethyl cellulose,carboxymethylcellulose, and polyvinyl alcohol. In the manufacturingmethod of the zeolite structure of the present embodiment, hydroxypropylmethylcellulose or hydroxyethyl methylcellulose can preferably be used.Such an organic binder has a high compatibility with the aqueous basicaluminum chloride solution, whereby the function of the organic binderis not easily disturbed. The water retention properties of the zeoliteraw material can satisfactorily be kept.

Furthermore, the zeolite raw material may further contain a dispersantand the like. Examples of the dispersant include fatty acid, acrylicacid, sorbitan acid, dextrin and polyalcohol.

There is not any special restriction on a method of mixing the zeoliteraw material containing at least the zeolite particles, the inorganicbinding material and the organic binder, and a known method can beemployed. Examples of the method include a method of mixing and kneadingthe material by using a twin arm type kneader manufactured by HondaMachinery Works Co., Ltd. in a dry system (i.e., without adding anywater) for 10 to 30 minutes, further adding water to the mixed material,and mixing and kneading the material for 20 to 60 minutes whileregulating viscosity of the mixed material.

(2-2) Extrusion Forming Step:

Next, the obtained zeolite raw material is formed in a predeterminedshape by extrusion, to obtain a formed zeolite article. It is to benoted that when the formed zeolite article is formed in a honeycombshape, for example, first the zeolite raw material is preferably kneadedto obtain a columnar formed article, and the columnar formed article isformed as a formed zeolite article having the honeycomb shape byextrusion. There is not any special restriction on a method of kneadingthe zeolite raw material (the forming raw material) to obtain thecolumnar formed article, and examples of the method include methodsusing a kneader, a vacuum clay kneader and the like. During theextrusion forming, it is preferable to use a die having the desirablewhole shape, cell shape, partition wall thickness, cell density and thelike. As a material of the die, a metal which is not easily worn ispreferable.

The obtained formed article having the honeycomb shape is preferablydried before fired. There is not any special restriction on a dryingmethod, and examples of the method include electromagnetic heatingsystems such as microwave heating drying and high frequency inductiveheating drying, and external heating systems such as hot air drying andsuperheated steam drying. Among these methods, there is a method ofdrying the article to remove a predetermined amount of water by theelectromagnetic heating system and then drying the article to remove theremaining water by the external heating system, and this method ispreferable in that the whole formed article can quickly and uniformly bedried so as to prevent cracks from being generated. In particular, whensuch drying is performed, the aqueous basic aluminum chloride solutionis dried to remove water from the inorganic binding material byevaporation, whereby the inorganic binding material becomes dense.

Moreover, before firing (finally firing) the formed zeolite article, theformed zeolite article is preferably calcinated. The article iscalcinated to degrease the article. There is not any special restrictionon this method, as long as contained organic substances (the organicbinder, the dispersant, and the like.) can be removed. As calcinatingconditions, the article is preferably heated at about 200 to 500° C. inan oxidizing atmosphere for about one to 20 hours.

(2-3) Firing Step:

Next, the formed zeolite article is fired to obtain a zeolite structurehaving a predetermined shape. Therefore, “the fired and formed zeolitearticle” is “the zeolite structure”. There is not any specialrestriction on a firing method, and the article can be fired by using anelectric furnace, a gas furnace or the like. Firing conditions arepreferably heating at a temperature from 500 to 750° C. in theatmosphere for one to ten hours.

When the drying and firing steps are performed in this manner and thezeolite particles bind with the inorganic binding material, a basicaluminum chloride solution (the aqueous basic aluminum chloridesolution) included as the inorganic binding material dries to form abinding portion, whereby the denser binding portion can be formed. Inconsequence, the average pore diameter of gaps formed by the inorganicbinding material, i.e., pores formed in the porous article increases,and it is possible to satisfy the relation of the above equation (1), inwhich P2 is a ratio of volumes Vb of pores having pore diameters of0.003 to 0.03 μm with respect to the whole pore volume Va of the zeolitestructure, and P1 is a ratio of a volume V2 of the inorganic bindingmaterial in the zeolite structure with respect to a volume V1 of thezeolite structure. Moreover, the inorganic binding material itself bindsthe respective particles more densely, and hence a binding portion bythe inorganic binding material becomes thick, whereby the mechanicalstrength, for example, the bending strength of the zeolite structureconstituted of the porous article becomes remarkably high. It is to benoted that the binding portion (the inorganic binding material) of basicaluminum chloride formed by drying is the binding portion made ofaluminum oxide through the firing step.

Moreover, when the zeolite particles subjected to the ion exchangetreatment are not used as the zeolite particles, the fired and formedzeolite article may be subjected to the ion exchange treatment betweencations of zeolite and the metal ions.

EXAMPLES

Hereinafter, the present invention will further specifically bedescribed with respect to examples, but the present invention is notlimited to these examples.

Example 1

As zeolite particles, there were prepared zeolite particles made ofβ-type zeolite, subjected to 3 mass % ion exchange between cations ofzeolite and copper ions and having an average particle diameter of 0.7μm.

Moreover, as inorganic binding materials, there were prepared a basicaluminum chloride solution containing 32 mass % of basic aluminumchloride (“Takibine #1500 (trade name)” manufactured by Taki ChemicalCo., Ltd.) and boehmite having a specific surface area of 130 m²/g.

To 3500 g of zeolite particles composed of the above β-type zeoliteparticles, as the inorganic binding materials, 1750 g of the above basicaluminum chloride solution (the mass of basic aluminum chloride was 560g) and 940 g of boehmite were added as described above. The volume ofthe fired inorganic binding material corresponded to 16.4 vol % withrespect to the volume of a zeolite structure to be obtained. Moreover,the amount of basic aluminum chloride corresponded to 16.0 mass % interms of a solid content with respect to 100 mass % of the zeoliteparticles. It is to be noted that the volume of the fired inorganicbinding material was beforehand obtained by individually firing theinorganic binding materials used in the present example and measuring amass change ratio due to the firing. The mass change ratio due to thefiring of the basic aluminum chloride solution was 23.5%, and thedensity of the fired material was 3.20 g/cm³. Moreover, boehmite had amass change ratio of 82.2%, and a density of 3.18 g/cm³ after thefiring. It is to be noted that the mass change ratio due to the firingof the zeolite particles was 0.0% (no mass change), and the density was1.85 g/cm³.

Next, further to the above mixed material, as an organic binder, 350 gof hydroxypropyl methylcellulose (HPMC) was added. The materials weremixed by using a twin arm type kneader manufactured by Honda MachineryWorks Co., Ltd. in a dry system for ten minutes, water was furtheradded, and the material was mixed and kneaded for 40 minutes whileregulating viscosity of the mixed material, thereby obtaining a kneadedsubstance of zeolite (a zeolite raw material). Table 1 indicates ablending prescription of the zeolite raw material.

The obtained kneaded zeolite substance was extruded with a continuouskneading vacuum extrusion forming machine manufactured by HondaMachinery Works Co., Ltd., to extrusion-form a plate-like materialhaving a width of 25 mm and a thickness of 5 mm, thereby obtaining aformed zeolite article. The obtained formed zeolite article was driedwith a hot air drier at 80° C. for 12 hours, degreased in a firingfurnace at 450° C. for five hours, and fired at 700° C. for four hours,to obtain a fired zeolite article (a zeolite structure).

It is to be noted that an average particle diameter of zeolite particlesis a median diameter (d50) in a distribution of particle diameters ofpowder containing zeolite particles. The diameter was measured by alaser diffraction scattering process in conformity to JIS R1629.

Moreover, the specific surface area which was BET specific surface areawas measured by using a flow type specific surface area measuringdevice: “FlowSorb-2300 (trade name)” manufactured by Micromeritics, Inc.and a sample pretreatment where a sample was held at 200° C. for tenminutes was measured. Here, the specific surface area is the surfacearea per unit mass indicating a value obtained by obtaining a moleculenumber (N) necessary for covering the surface of the sample with amonomolecular layer of a gas adsorbed in the surface of the sample, forexample, by gas physical adsorption with B.E.T principle, multiplyingthis adsorption molecular number (N) by a molecule sectional area of theadsorbed gas to obtain the surface area of the sample, and dividing thesurface area of this sample by the mass of the sample.

Furthermore, the obtained zeolite structure was subjected to afour-point bending test in conformity to JIS R1601, to measure a bendingstrength of the zeolite structure. Table 2 indicates the measurementresult of the bending strength. Moreover, column “fine pore ratio P2” ofTable 2 means a ratio P2 of volumes Vb of pores having pore diameters of0.003 to 0.03 μm with respect to the whole pore volume Va of the zeolitestructure, and column “inorganic binding material ratio P1” means aratio P1 of a volume V2 of the inorganic binding material in the zeolitestructure with respect to a volume V1 of the zeolite structure.Furthermore, column “P2/P1” means a value (P2/P1) of a ratio of the finepore ratio P2 with respect to the inorganic binding material ratio P1.It is to be noted that the above meanings of the columns also apply toTable 4.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Zeolite 3500g  3500 g 3500 g  3500 g  3500 g particle Basic 1750 g  1150 g 3000 g 1150 g  3000 g aluminum (560 g)  (368 g) (960 g) (368 g)  (960 g)chloride solution (basic aluminum chloride) Boehmite 940 g 1100 g 580 g530 g — HPMC 350 g  350 g 350 g 350 g  350 g

TABLE 2 Example 1 Example 2 Example 3 Example 4 Example 5 Strength 5.04.5 5.7 3.2 5.3 (MPa) Fine pore 10.9% 15.0% 7.5% 9.1% 3.0% ratio P2Inorganic 16.4% 16.3% 16.4% 10.5% 10.4% binding material ratio P1 P2/P10.66 0.92 0.46 0.87 0.29 Mass ratio of 16.0% 10.5% 27.4% 10.5% 27.4%basic aluminum chloride

Example 2

As shown in Table 1, a zeolite structure was manufactured and a bendingstrength thereof was measured in the same manner as in Example 1 exceptthat as an inorganic binding material, 1150 g of basic aluminum chloridesolution (a mass of basic aluminum chloride was 368 g) and 1100 g ofboehmite were added. The measurement results are shown in Table 2. It isto be noted that a volume of the fired inorganic binding material was anamount corresponding to 16.3 vol % with respect to the volume of thezeolite structure. Moreover, basic aluminum chloride had an amountcorresponding to 10.5 mass % in terms of a solid content with respect to100 mass % of the zeolite particles.

Example 3

As shown in Table 1, a zeolite structure was manufactured and a bendingstrength thereof was measured in the same manner as in Example 1 exceptthat as an inorganic binding material, 3000 g of basic aluminum chloridesolution (a mass of basic aluminum chloride was 960 g) and 580 g ofboehmite were added. The measurement results are shown in Table 2. It isto be noted that a volume of the fired inorganic binding material was anamount corresponding to 16.4 vol % with respect to the volume of thezeolite structure. Moreover, basic aluminum chloride had an amountcorresponding to 27.4 mass % in terms of a solid content with respect to100 mass % of the zeolite particles.

Example 4

As shown in Table 1, a zeolite structure was manufactured and a bendingstrength thereof was measured in the same manner as in Example 1 exceptthat as an inorganic binding material, 1150 g of basic aluminum chloridesolution (a mass of basic aluminum chloride was 368 g) and 530 g ofboehmite were added. The measurement results are shown in Table 2. It isto be noted that a volume of the fired inorganic binding material was anamount corresponding to 10.5 vol % with respect to the volume of thezeolite structure. Moreover, basic aluminum chloride had an amountcorresponding to 10.5 mass % in terms of a solid content with respect to100 mass % of the zeolite particles.

Example 5

As shown in Table 1, a zeolite structure was manufactured and a bendingstrength thereof was measured in the same manner as in Example 1 exceptthat as an inorganic binding material, 3000 g of basic aluminum chloridesolution (a mass of basic aluminum chloride was 960 g) was added. Themeasurement results are shown in Table 2. It is to be noted that avolume of the fired inorganic binding material was an amountcorresponding to 10.4 vol % with respect to the volume of the zeolitestructure. Moreover, basic aluminum chloride had an amount correspondingto 27.4 mass % in terms of a solid content with respect to 100 mass % ofthe zeolite particles.

Comparative Example 1

As shown in Table 3, a zeolite structure was manufactured and a bendingstrength thereof was measured in the same manner as in Example 1 exceptthat as an inorganic binding material, any basic aluminum chloridesolution was not used and 1440 g of boehmite was added. The measurementresults are shown in Table 4. It is to be noted that a volume of thefired inorganic binding material was an amount corresponding to 16.5 vol% with respect to the volume of the zeolite structure.

Comparative Example 2

As shown in Table 3, a zeolite structure was manufactured and a bendingstrength thereof was measured in the same manner as in Example 1 exceptthat as an inorganic binding material, 900 g of basic aluminum chloridesolution (a mass of basic aluminum chloride was 288 g) and 1200 g ofboehmite were added. The measurement results are shown in Table 4. It isto be noted that a volume of the fired inorganic binding material was anamount corresponding to 16.5 vol % with respect to the volume of thezeolite structure. Moreover, basic aluminum chloride had an amountcorresponding to 8.2 mass % in terms of a solid content with respect to100 mass % of the zeolite particles.

Comparative Example 3

As shown in Table 3, a zeolite raw material was prepared in the samemanner as in Example 1 except that as an inorganic binding material,3500 g of basic aluminum chloride solution (a mass of basic aluminumchloride was 1120 g) and 450 g of boehmite were added. However, inComparative Example 3, the zeolite raw material had low water retentionproperties, and the zeolite raw material could not be extruded toprepare a formed article. It is to be noted that a volume of the firedinorganic binding material was an amount corresponding to 16.5 vol %with respect to a volume of a zeolite structure. Moreover, basicaluminum chloride had an amount corresponding to 32.0 mass % in terms ofa solid content with respect to 100 mass % of the zeolite particles.

Comparative Example 4

As shown in Table 3, a zeolite structure was prepared and a bendingstrength thereof was measured in the same manner as in Example 1 exceptthat as an inorganic binding material, 900 g of basic aluminum chloridesolution (a mass of basic aluminum chloride was 288 g) and 600 g ofboehmite were added. The measurement results are shown in Table 4. It isto be noted that a volume of the fired inorganic binding material was anamount corresponding to 10.5 vol % with respect to the volume of thezeolite structure. Moreover, basic aluminum chloride had an amountcorresponding to 8.2 mass % in terms of a solid content with respect to100 mass % of the zeolite particles.

Comparative Example 5

As shown in Table 3, a zeolite structure was prepared and a bendingstrength thereof was measured in the same manner as in Example 1 exceptthat as an inorganic binding material, 1150 g of basic aluminum chloridesolution (a mass of basic aluminum chloride was 368 g) and 350 g ofboehmite were added. The measurement results are shown in Table 4. It isto be noted that a volume of the fired inorganic binding material was anamount corresponding to 8.5 vol % with respect to the volume of thezeolite structure. Moreover, basic aluminum chloride had an amountcorresponding to 10.5 mass % in terms of a solid content with respect to100 mass % of the zeolite particles.

TABLE 3 Comp. Comp. Comp. Ex Ex Comp. Ex Comp. Ex Ex 1 2 3 4 5 Zeoliteparticles 3500 g 3500 g 3500 g 3500 g  3500 g  Basic aluminum —  900 g3500 g 900 g 1150 g  chloride solution  (288 g) (1120 g) (288 g) (368 g)(basic aluminum chloride) Boehmite 1440 g 1200 g  450 g 600 g 350 g HPMC 350 g  350 g  350 g 350 g 350 g

TABLE 4 Comp. Comp. Comp. Comp. Ex Ex 1 Ex 2 Comp. Ex 3 Ex 4 5 Strength(MPa) 3.2 3.5 Extrusion 2.6 0.9 cannot be performed Fine pore ratio30.0% 17.6% — 11.3% 8.6% P2 Inorganic 16.5% 16.5% 16.5% 10.5% 8.5%binding material ratio P1 P2/P1 1.82 1.07 — 1.08 1.01 Mass ratio of —8.2% 32.0% 8.2% 10.5% basic aluminum chloride

It is seen from Table 2 and Table 4 that the zeolite structures ofExamples 1 to 5 have a high bending strength. In the zeolite structureconstituted of the zeolite particles and the inorganic binding material,as the amount of the inorganic binding material is large, the strengthimproves. On the other hand, if the amount of the inorganic bindingmaterial is excessively large, the ratio of the zeolite particlesbecomes small, and performance such as purification performance lowers.Here, it is seen that the zeolite structures of Examples 1 to 3 andComparative Examples 1 to 3 contain substantially the same degree of theinorganic binding material having the inorganic binding material ratioP1 in a range of 16.3 to 16.5 vol %, but as compared with the zeolitestructures of Comparative Examples 1 and 2, the zeolite structures ofExamples 1 to 3 have a high bending strength. In the zeolite structuresof Examples 1 to 3, in the zeolite raw material, the inorganic bindingmaterial including a predetermined amount of basic aluminum chloride isused. It is supposed that basic aluminum chloride forms a dense bindingportion, to improve the bending strength. It is to be noted that in thezeolite structures of Examples 1 to 3, the value (P2/P1) of the ratio ofthe fine pore ratio P2 with respect to the inorganic binding materialratio P1 is 1.0 or less, and it is seen from this value that the densebinding portion is formed. In particular, when the mass ratio of basicaluminum chloride is 10 mass %, the value of “P2/P1” is 1.0 or less. Itis to be noted that in Comparative Example 3, since the extrusion couldnot be performed, the zeolite structure could not be manufactured,whereby the value of “P2/P1” could not be calculated.

Moreover, Examples 4 and 5 and Comparative Example 4 containsubstantially the same degree of the inorganic binding material havingthe inorganic binding material ratio P1 in a range of 10.4 to 10.5 vol%. However, Examples 4 and 5 having a value “P2/P1” of 1.0 or less havea high bending strength, whereas Comparative Example 4 having a value“P2/P1” of 1.08 has a low bending strength. Moreover, it is seen thatwhen the inorganic binding material ratio P1 is less than 10 vol %(specifically, 8.5 vol %) as in Comparative Example 5, the bendingstrength of the zeolite structure noticeably lowers. It is to be notedthat when the Example 4 is compared with Comparative Example 2,Comparative Example 2 has a higher bending strength. However, Example 4and Comparative Example 2 have different inorganic binding materialratios P1 (i.e., the amount of the zeolite particles). Therefore, asdescribed above, both the examples cannot simply be compared only by thebending strength. That is, in Comparative Example 2, as compared withExample 4, the amount of the zeolite particles is relatively small, andhence various properties such as the purification performance due tozeolite deteriorate.

A zeolite structure of the present invention can be used in an adsorbingmaterial, a catalyst, a catalyst carrier, a gas separation film or anion exchanger. In particular, the zeolite structure can preferably beutilized to purify an exhaust gas discharged from an engine for a car,an engine for a construction machine, an industrial stational engine, aburning apparatus or the like and containing NOx or the like.

DESCRIPTION OF REFERENCE NUMERALS

1: partition wall, 2: cell, 4: outer peripheral wall, 11: one end, 12:the other end, 32 zeolite particles, 33: inorganic binding material, 35:pore and 100 and 100 a: zeolite structure.

What is claimed is:
 1. A zeolite structure obtained by firing a formedarticle obtained by extruding a zeolite raw material containing zeoliteparticles and an inorganic binding material including at least basicaluminum chloride and being porous, wherein a ratio P1 (P1=V2/V1×100) ofa volume V2 of the fired inorganic binding material in the zeolitestructure with respect to a volume V1 of the zeolite structure is from10 to 50%, and a relation of equation (1) is satisfied:P2/P1≦1.0  (1), in which P1 is the ratio of the volume V2 of the firedinorganic binding material in the zeolite structure with respect to thevolume V1 of the zeolite structure and P2 (P2=Vb/Va×100) is a ratio ofvolumes Vb of pores having pore diameters of 0.003 to 0.03 μm withrespect to the whole pore volume Va of the zeolite structure.
 2. Thezeolite structure according to claim 1, wherein the inorganic bindingmaterial contained in the zeolite raw material includes basic aluminumchloride having an amount corresponding to 10 to 30 mass % in terms of asolid content with respect to 100 mass % of the zeolite particles. 3.The zeolite structure according to claim 2, wherein the inorganicbinding material contained in the zeolite raw material further includesat least one type selected from the group consisting of alumina sol,silica sol, titania sol, zirconia sol, ceria sol, boehmite,montmorillonite, hydrotalcite, hydraulic alumina, silicon resin, andwater glass.
 4. The zeolite structure according to claim 3, whereinzeolite particles of at least a part of the zeolite particles areparticles made of at least one type of zeolite selected from the groupconsisting of ZSM-5 type zeolite, β-type zeolite, Y-type zeolite,mordenite type zeolite and ferrierite type zeolite.
 5. The zeolitestructure according to claim 4, wherein zeolite particles of at least apart of the zeolite particles are particles made of zeolite subjected toion exchange between cations of zeolite and ions of at least one metalselected from the group consisting of copper, iron, nickel, zinc,manganese, cobalt, silver, palladium, indium, cerium, gallium, titaniumand vanadium.
 6. The zeolite structure according to claim 3, whereinzeolite particles of at least a part of the zeolite particles areparticles made of zeolite subjected to ion exchange between cations ofzeolite and ions of at least one metal selected from the groupconsisting of copper, iron, nickel, zinc, manganese, cobalt, silver,palladium, indium, cerium, gallium, titanium and vanadium.
 7. Thezeolite structure according to claim 2, wherein zeolite particles of atleast a part of the zeolite particles are particles made of at least onetype of zeolite selected from the group consisting of ZSM-5 typezeolite, β-type zeolite, Y-type zeolite, mordenite type zeolite andferrierite type zeolite.
 8. The zeolite structure according to claim 7,wherein zeolite particles of at least a part of the zeolite particlesare particles made of zeolite subjected to ion exchange between cationsof zeolite and ions of at least one metal selected from the groupconsisting of copper, iron, nickel, zinc, manganese, cobalt, silver,palladium, indium, cerium, gallium, titanium and vanadium.
 9. Thezeolite structure according to claim 2, wherein zeolite particles of atleast a part of the zeolite particles are particles made of zeolitesubjected to ion exchange between cations of zeolite and ions of atleast one metal selected from the group consisting of copper, iron,nickel, zinc, manganese, cobalt, silver, palladium, indium, cerium,gallium, titanium and vanadium.
 10. The zeolite structure according toclaim 1, wherein the inorganic binding material contained in the zeoliteraw material further includes at least one type selected from the groupconsisting of alumina sol, silica sol, titania sol, zirconia sol, ceriasol, boehmite, montmorillonite, hydrotalcite, hydraulic alumina, siliconresin, and water glass.
 11. The zeolite structure according to claim 10,wherein zeolite particles of at least a part of the zeolite particlesare particles made of at least one type of zeolite selected from thegroup consisting of ZSM-5 type zeolite, β-type zeolite, Y-type zeolite,mordenite type zeolite and ferrierite type zeolite.
 12. The zeolitestructure according to claim 11, wherein zeolite particles of at least apart of the zeolite particles are particles made of zeolite subjected toion exchange between cations of zeolite and ions of at least one metalselected from the group consisting of copper, iron, nickel, zinc,manganese, cobalt, silver, palladium, indium, cerium, gallium, titaniumand vanadium.
 13. The zeolite structure according to claim 10, whereinzeolite particles of at least a part of the zeolite particles areparticles made of zeolite subjected to ion exchange between cations ofzeolite and ions of at least one metal selected from the groupconsisting of copper, iron, nickel, zinc, manganese, cobalt, silver,palladium, indium, cerium, gallium, titanium and vanadium.
 14. Thezeolite structure according to claim 1, wherein zeolite particles of atleast a part of the zeolite particles are particles made of at least onetype of zeolite selected from the group consisting of ZSM-5 typezeolite, β-type zeolite, Y-type zeolite, mordenite type zeolite andferrierite type zeolite.
 15. The zeolite structure according to claim14, wherein zeolite particles of at least a part of the zeoliteparticles are particles made of zeolite subjected to ion exchangebetween cations of zeolite and ions of at least one metal selected fromthe group consisting of copper, iron, nickel, zinc, manganese, cobalt,silver, palladium, indium, cerium, gallium, titanium and vanadium. 16.The zeolite structure according to claim 1, wherein zeolite particles ofat least a part of the zeolite particles are particles made of zeolitesubjected to ion exchange between cations of zeolite and ions of atleast one metal selected from the group consisting of copper, iron,nickel, zinc, manganese, cobalt, silver, palladium, indium, cerium,gallium, titanium and vanadium.
 17. The zeolite structure according toclaim 1, which is formed in a honeycomb shape including partition wallsdisposed to form a plurality of cells which become through channels of afluid and which extend from one end face to the other end face.